What is the cell morphology of Mycobacterium tuberculosis?
M. tuberculosis is an obligate aerobe ( weakly Gram-positive mycobacterium, hence Ziehl-Neelsen staining (Acid-fast staining) is used). While mycobacteria do not seem to fit the Gram-positive category from an empirical standpoint (i.e., they do not retain the crystal violet stain), they are classified as an acid-fast Gram-positive bacterium due to their lack of an outer cell membrane. M. tuberculosis divides every 15 to 20 hours, which is extremely slow compared to other bacteria, which tend to have division times measured in minutes (for example, E. coli can divide roughly every 20 minutes). It is a small bacillus that can withstand weak disinfectants and can survive in a dry state for weeks.
